Process for dry cooling of coke with steam with subsequent use of the synthesis gas produced

ABSTRACT

A method for the dry quenching of coke using steam with subsequent use of the synthesis gas generated, the method involving the cyclic coking of coal to coke with the coke being sent to a quenching device after being discharged from the coke oven and steam being introduced into the quenching device for dry quenching, thus creating synthesis gas made up of carbon monoxide (CO) and hydrogen (H 2 ) via a water-gas reaction, and the synthesis gas produced being fed to a further application. This method allows the heat generated during coking to be used for the production of useful synthesis gas which, in turn, can be used for a further purpose or in the heating process, thus on the whole achieving an extremely even energy balance throughout the entire process.

The invention relates to a method for the dry quenching of coke by meansof steam with subsequent use of the synthesis gas generated, said methodinvolving the cyclic coking of coal to coke with the coke being sent toa quenching device after being discharged from the coke oven and steambeing introduced into the quenching device for dry quenching, thuscreating synthesis gas made up of carbon monoxide (CO) and hydrogen (H₂)via a water-gas reaction, and the synthesis gas produced being fed to afurther application. This method allows the heat generated during cokingto be used for the production of useful synthesis gas which, in turn,can be used for a further purpose or used in the heating process, thuson the whole achieving an extremely even energy balance throughout theentire process.

Most methods for the production of coke take place in large coke ovenbatteries or coke oven banks that comprise conventional coke ovenchambers or coke oven chambers of the “heat recovery” or “non-recovery”type. In conventional coke oven chambers the coking gas is collected andprocessed, while the coking gas in “heat recovery” or“non-recovery”-type coke oven banks is combusted in the coke oven inorder to heat said oven. Here, in many embodiments the heating of thecoke oven is carried out in several steps in a gas space above the cokecake and in a coke oven sole below the coke oven chamber.

The coking process is performed cyclically, the cycles being charging,coking, discharging and quenching. After coking, the coke is pushed outof the coke oven chamber at a temperature of approximately 1100° C. Itis pushed out into a quenching car that collects the coke cake andtransports it to a quenching device. In many embodiments this is a wetquench tower, where the coke cake is sprayed with water which evaporatesand cools the coke cake to a temperature below the kindling temperatureof the coke so that it can be transported in the open air without posinga hazard. After quenching, the temperature of the coke is unevenlydistributed in the coke cake but is usually less than 100° C.

DE19614482C1 gives one embodiment of a wet quench tower. This teachingdescribes a plant for the wet quenching of hot coke in a process for thecoking of coal using a coke sluice and a coke transfer chute that islocated in a quench tower with a water feed device. On the other side,the chute fits onto a coke quenching car equipped at the bottom end witha coke discharge device and water discharge flaps. The water feed systemis located directly at the transfer chute and empties into the cokequenching car, which can be sealed watertightly, and said car isequipped with a control system which keeps the coke discharge flapsclosed watertightly while the water is being fed in and opens the waterdischarge flaps once the water feed has been completed. When water isused for quenching, all of the thermal energy stored in the coke cake islost without being used.

For this reason, increasing efforts have recently been made to dryquench hot coke using gases instead of water. Here, the gases are passedthrough the hot coke and collected or extracted until the coke hascooled to a temperature below its kindling temperature. The hot gas isusually passed through a heat recovery unit in which steam is generated,thus recovering the thermal energy. In turn, the steam can be used todrive auxiliary units or to generate electric power. For these purposes,inert gases, such as nitrogen or blast furnace gas, are often used.

WO9109094B1 describes a method for the dry quenching of coke in aquenching chamber with the aid of circulating quenching gas, said methodallowing the velocity of the gas corning from the coke to be adjusted sothat the grain size of the entrained coke dust particles is less than 3mm and when the hot quenching gas enters the waste heat recovery boilerthe grain size of the entrained coke dust is less than 1 mm, said methodinvolving this gas being passed through a device that consists of aquenching chamber and an antechamber with a round cross section of aboutequal size and a cylindrical outer casing made of metal, and inparticular the roof of the quenching chamber being in an inclinedposition so that it rises to the hot gas channel, thus increasing thecross section of the annular gas channel above the coke pile enough toallow the gas velocity of the hot quenching gas to be adjusted duringquenching so that it remains virtually uniform across the length.

WO8602939A1 describes a method for dry coke quenching using quenchinggas, said method involving the coke and the quenching gas being fed incountercurrent direction through a two-stage quencher, the first stageinvolving quenching to coke temperatures of approximately 800° C. andthe quenching gas fed through the second quenching stage containingsteam, the quenching gas loop thus being directly coupled with a thermaltreatment step in which steam is added so that there is essentially nochar burnout, which is achieved by the quenching in the first quenchingstage taking place solely by indirect heat exchange between the coke anda coolant via heat exchanger walls and the quenching in the second stagebeing carried out solely by means of the steam-containing quenching gas.

State-of-the-art methods for dry coke quenching may include a variety ofembodiments. EP0317752A2 describes a method for improving theperformance of coke dry quenchers which involves hot coke being brokenup before entering the quenching shaft. DE3030969A1 describes a methodfor the dry quenching of hot raw coke that is pushed out of the chambersof a coke oven battery and discharged in a quenching chamber, where itis quenched by means of direct or indirect contact, or both, with aquenching agent, and therefore the raw coke is preclassified into two ormore size fractions before entering the quenching chamber and theindividual size fractions are subjected to quenching in separatequenching chambers.

Further embodiments relate to the heat recovery or cleaning of thequenching gas. DE2435500A1 describes a method for preheating coking coalusing superheated waste heat steam which is generated in a dry cokequencher by the coke releasing, at its highest temperature level, someof its heat to the walls of a steam jacket. DE3217146A1 describes adevice for dedusting the loop gas of a coke dry quencher in which thegas inlet channel and the gas outlet channel are located at right anglesto each other, the gas outlet channel being directly connected, via aconical expansion, with the inlet opening of the waste heat recoveryboiler integrated into the gas loop and a dust collection chamber withan inclined dust discharge area being positioned on the opposite side tothe gas inlet channel.

However, the said methods and their embodiments have the disadvantagethat during quenching the heat of the coke either cannot be recovered orthe heat of the coke can only be inefficiently recovered as duringquenching a large gas volume is generated and this needs to be passedthrough a heat recovery unit, making quenching technically difficult oreconomically inefficient. For this reason, it would be advantageous toutilise the heat that exists in the pushed coke via an endothermicchemical reaction that makes this energy available in chemical form.

One suitable endothermic chemical reaction is the water-gas reactionwith the corresponding water-gas equilibrium. To carry out thisreaction, steam (H₂O) is passed through the hot coke, which reacts withthe steam (H₂O) to form hydrogen (H₂) and carbon monoxide (CO). Thisreaction is endothermic and reads:

C+H₂O

H₂+CO; ΔH=+131.3 kj/mol

An additional reaction between the steam and the coke to form carbondioxide and two equivalents of hydrogen is possible but according to theinvention it does not generally take place due to suitable metering anda suitable gas velocity of the steam. This reaction is stronglyendothermic and can only be carried out with additional heating of thecoke.

GB347601A describes a method for the production of a gas mixture made upof nitrogen and hydrogen which is suitable for the synthesis of ammoniaand which is produced in a coke quenching device in which the coke issprayed with water and permeated by air and in which the carbon monoxideis directed into a plant section in which the carbon monoxide isconverted into an equivalent of hydrogen via a subsequent conversion ofthe carbon monoxide using steam. Here, the steam for converting thecarbon monoxide comes from the water that is sprayed into the coke cakein order to quench the coke. The application does not describe quenchingthe coke cake with permeating gaseous steam.

Therefore, the objective is to provide a method that cyclicallycarbonises coal and uses gaseous steam (H₂O) to dry quench hot cokeafter a coking cycle, with the steam (H₂O) thus reacting at leastpartially with the coke to form hydrogen (H₂) and carbon monoxide (CO)according to the water-gas equilibrium, the hydrogen (H₂) obtained beingcollected and the gas mixture thus obtained being used for a furtherpurpose. In this way synthesis gas is obtained.

According to the invention, coke quenching using steam takes place in aquenching device that is preferably designed as a quenching shaft.Following coking of the coal and completion of the coking process, thecoke cake is taken to, or tipped onto, a quenching car, which transportsthe coke cake to the quenching device. Here, the coke cake is sealed offfrom the surrounding atmosphere and gaseous steam is passed through it.Preferably, this is done in a vertically upward gas flow direction sothat the specifically heavier steam is displaced by the lighter hydrogenduring the quenching process. The steam may be a gas mixture in anystate and even be in a mixture with other gases, but it is preferablyused in pure form.

What is claimed in particular is a method for the dry quenching of coke,in which

-   -   coal is heated in a coke oven via heating by means of a high        calorific gas and coke is obtained via cyclic coking, said coke        being pushed out into a coke quenching car on completion of the        coking, and    -   the incandescent coke is transported to a coke quenching device        in a coke quenching car in which said incandescent coke is        quenched to a temperature below the kindling temperature by        means of a quenching gas,

and said process being characterised in that

-   -   gaseous steam (H₂O) is used as the quenching gas under the        exclusion of air, said steam reacting at least partially with        the incandescent coke (C) according to the water-gas reaction to        form synthesis gas made up of hydrogen (H₂) and carbon monoxide        (CO), and    -   due to the dry quenching being carried out in a coke quenching        device the hydrogenous quenching gas obtained is collected, and    -   the gas mixture thus obtained is used for a further purpose.

The synthesis gas generated may also contain impurities, but if thereaction is carried out correctly, it consists mainly of theconstituents hydrogen (H₂) and carbon monoxide (CO).

For implementing the method the steam is preferably generated in a steamboiler. Said steam is kept hot through suitable possibilities forintermediate storage and is then fed into the coke quenching deviceunder pressure using a metering device. In order to prevent condensationof the steam on introduction into the coke quenching device, the feedpipes can, in an advantageous embodiment, be heated. When the steamreacts with the hot coke, hydrogen (H₂) and carbon monoxide (CO) areproduced. In a preferred embodiment the gaseous steam used is dry, i.e.there are no adhering water droplets or mist. Via the method accordingto the invention the thermal energy of the coke that is released duringquenching following the coking process is used to generate usefulproducts. As a result, the energy balance of the overall coke productionprocess can be improved.

The synthesis gas generated and the hydrogen contained therein can beused for any further purpose. In one embodiment of the invention use ofthis gas mixture for a further purpose involves it being added to thefuel gas of the coke oven(s). In this way, the coke oven is heated withthe gas generated during quenching of the coke. For this, the hydrogenused to heat the coke oven can be mixed with a hydrocarbonaceous fuelgas before being fed to the coke oven. In an exemplary embodiment thefuel gas is natural gas. In a further embodiment, the fuel gas is cokeoven gas. It is also possible to use blast furnace gas from a blastfurnace process as the fuel gas instead of a hydrocarbonaceous fuel gas.

In an further embodiment the synthesis gas is subjected to a heatrecovery process before being used for a further purpose or being fed tothe coke oven for heating purposes. This may, for example, be achievedby passing the gas through a waste heat recovery boiler. In oneembodiment of the invention steam is generated during the heat recoveryprocess. In a typical embodiment the steam is then used to generatemechanical energy by driving a turbine. This can, in turn, be used togenerate electric power. It is also possible to direct the synthesis gasgenerated through a heat exchanger in which the steam used for quenchingis preheated in countercurrent direction.

In a further embodiment of the invention a water-gas shift reaction iscarried out to convert the carbon monoxide (CO) into carbon dioxide(CO₂) after the coke has been quenched with steam (H₂O). As a result, agas mixture is obtained. This gas mixture mainly consists of hydrogen(H₂) and carbon dioxide (CO₂) and can be easily converted into purehydrogen, for example by means of pressure-swing adsorption. Here, inone embodiment the steam required for this can be added in excess to thequenching process or added to the synthesis gas already generated. Itmay also be sprayed in as liquid water after the coke has been quenched.

In a further embodiment of the invention use for a further purposerelates to a conversion of the carbon monoxide with steam and subsequentpurification of the hydrogen obtained during the conversion in apressure-swing adsorption unit. The hydrogen can then be used, forexample, in a chemical process in a subsequent application.Pressure-swing adsorption units for the purification of hydrogen fromhydrogenous gases are well-known in the state of the art. WO2006066892A1teaches one example of a method for purifying hydrogen by means ofpressure-swing adsorption.

In a further embodiment of the invention the steam is split into atleast two part streams for quenching. In one embodiment of the inventiona part stream of the steam is introduced into the coke quenching devicefrom below in a vertically upward flow direction and a further partstream of the steam is fed into a part of the shaft in which the coke tobe quenched has a temperature of 500 to 900° C. This may, for example,be done via feed nozzles installed in the side of the shaft that injectthe steam directly into the coke.

In one exemplary embodiment of the invention the coke quenching deviceis a coke quenching shaft. In a further exemplary embodiment of theinvention the coke quenching device is a coke quenching chamber. Inaddition, this may, for example, be equipped with an antechamber. Thequenching device or the subsequent transfer line for the hydrogen mayalso be equipped with a dedusting device. This allows the dust to bereduced if a dust-laden coal is used or large amounts of dust arecreated during quenching.

For it to be used in implementing the method, the coke oven battery orcoke oven bank may be of any design and configured in any way. The cokeoven battery from which the coke comes and which is heated by thesynthesis gas may, for example, be a coke oven battery in which thecoking gas is collected and processed. The coke oven bank from which thecoke comes may, for example, be a “heat-recovery”-type coke ovenbattery. Finally, the coke oven bank from which the coke comes may alsobe a “nonrecovery”-type coke oven battery. Even the coke ovens that arelocated in a coke oven battery or bank may ultimately be of any designas long as they are suitable for the production of coke and for beingheated by synthesis gas when appropriate. The coke pushing may also becarried out at a different coke oven battery or bank from that to whichthe synthesis gas obtained during quenching is fed, but this is notusual practice.

Furthermore, auxiliary equipment, such as storage tanks for liquids orgases, pumps, valves, heating or quenching equipment, knock-out drums ormeters for measuring temperatures or concentrations of gas constituentsmay be used at any point in the method according to the invention.

The invention has the advantage of utilising the thermal energy of thecoke after coking by means of an endothermic chemical reaction and sothe thermal energy of the hot coke can be utilised much better than inprior-art methods. Furthermore, the invention has the advantage ofproviding hydrogen as a useful product without the addition of furtherenergy, thus allowing the energy balance of the overall method to beimproved. The environmental compatibility of this method can thus beconsiderably improved.

The invention is further explained by means of a drawing, this drawingmerely representing an exemplary embodiment and not being limitedthereto.

FIG. 1 shows a coke oven which serves to carbonise coal. It depicts thecoke oven chamber (1) with the coal cake (2), the coke oven chamberdoors (3), the primary heating space (4) above the coke cake (2) and thesecondary heating space (5) below the coke cake (2). The quenching car(6), which collects the coke cake (2) for quenching, is parked in frontof the coke oven chamber (1). Said quenching car (6) is brought in frontof the coke quenching chamber (7) and the coke cake (2) is emptied intothe coke quenching chamber (7) via a feed flap (7 a). Said flap (7 a) isclosed once the coke quenching chamber (7) has been filled. Steam (8,H₂O) then flows into the coke quenching chamber (7) from below andreacts with the hot coke cake (5 a) according to the water-gasequilibrium to form hydrogen and carbon monoxide (9, H₂ and CO) assynthesis gas. The steam (8) is generated via a steam boiler (10) with adownstream metering device (10 a). The synthesis gas (9) generatedduring quenching is extracted in an upwards direction and, followingdedusting in a dedusting unit (11), it is directed into the secondaryheating space (5) of the coke oven (1) as fuel gas (9 a). This is donevia a heat exchanger (12), which, in countercurrent direction, preheatsthe steam (8) fed in to quench the coke (2). Here, it is added to thepartially combusted coking gas which has already flowed into thesecondary heating space (5) from the primary heating space (4) andcombusted. As a result, it contributes to the heating of the coke cake(2) through the floor of the coke oven chamber (1). After combustion,the fully combusted coking gas is exported out of the secondary heatingspace (5) as waste gas (13) and sent to a gas scrubbing device (14). Thecleaned waste gas (14 a) is exported from the gas scrubbing device (13)and sent to a heat recovery unit (15). Here, a generator (15 a) thatgenerates electric power is driven via a turbine. The cooled waste gas(15 b) is exported via a flue (16). The quenched coke (5 a) or the coketo be quenched (5 a) is discharged via a discharge flap (7 b) and sentfor final quenching.

LIST OF REFERENCE NUMBERS AND DESIGNATIONS

-   1 Coke oven chamber-   2 Coal or coke cake-   3 Coke oven chamber doors-   4 Primary heating space-   5 Secondary heating space-   5 a Coke to be quenched-   6 Quenching car-   7 Coke quenching chamber-   7 a Feed flap-   7 b Discharge flap-   8 Steam-   9 Synthesis gas-   9 a Fuel gas for the secondary heating space-   10 Steam boiler-   10 a Control valve for steam-   11 Storage tank-   12 Heat exchanger-   13 Waste gas-   14 Gas scrubbing device-   14 a Cleaned waste gas-   15 Heat recovery unit-   15 a Generator-   15 b Cooled waste gas-   16 Flue

1. Method for the dry quenching of coke in which coal is heated in acoke oven via heating by means of a high calorific gas and coke isobtained via cyclic coking, said coke being pushed out into a cokequenching car on completion of the coking, and the incandescent coke istransported to a coke quenching device in a coke quenching car in whichsaid incandescent coke is quenched to a temperature below the kindlingtemperature by means of a quenching gas, wherein gaseous steam (H2O) isused as the quenching gas under the exclusion of air, said steamreacting at least partially with the incandescent coke according to thewater-gas reaction to form synthesis gas made up of hydrogen (H2) andcarbon monoxide (CO), and due to the dry quenching being carried out ina coke quenching device the hydrogenous quenching gas obtained iscollected, and the gas mixture thus obtained is used for a furtherpurpose.
 2. Method for the dry quenching of coke according to claim 1,wherein use for a further purpose relates to the gas mixture being addedto the fuel gas of the coke oven(s).
 3. Method for the dry quenching ofcoke according to claim 2, wherein a hydrocarbonaceous fuel gas is mixedwith the synthesis gas used to heat the coke oven before it is added tothe coke oven.
 4. Method for the dry quenching of coke according toclaim 3, wherein the fuel gas is natural gas.
 5. Method for the dryquenching of coke according to claim 3, wherein the fuel gas is cokeoven gas.
 6. Method for the dry quenching of coke according to claim 1,wherein the synthesis gas is subjected to a heat recovery process beforebeing used for a further purpose.
 7. Method for the dry quenching ofcoke according to claim 6, wherein steam is generated during the heatrecovery process.
 8. Method for the dry quenching of coke according toclaim 1, wherein use for a further purpose relates to conversion of thecarbon monoxide (CO) contained in the gas mixture using steam (H2O),said carbon monoxide (CO) being converted to carbon dioxide (CO2). 9.Method for the dry quenching of coke according to claim 8, wherein usefor a further purpose relates to conversion of the carbon monoxide (CO)using steam (H2O) and subsequent purification of the hydrogen (H2)obtained in a pressure-swing adsorption unit.
 10. Method for the dryquenching of coke according to claim 1, wherein the steam for quenchingis split into at least two part streams, with one part stream of thesteam being fed into the coke quenching device from below in avertically upward flow direction and a further part stream of the steambeing fed into a part of the coke quenching device in which the coke tobe quenched has a temperature of 500 to 900° C.
 11. Method for the dryquenching of coke according to claim 1, wherein the coke quenchingdevice is a coke quenching shaft.
 12. Method for the dry quenching ofcoke according to claim 1, wherein the coke quenching device is a cokequenching chamber.
 13. Method for the dry quenching of coke according toclaim 12, wherein the coke quenching chamber is equipped with anantechamber.